MIT/Aurora D8 Airliner and XD8 X-Plane

[overscan (PaulMM)]

This design, studied under NASA N+3 program, is getting continued funding.

Is it just me or is this (aside from T-tail) a copy of the Myasishchev M-60 configuration?

 

[flateric]

...Nord 600 (1965)

 

[overscan (PaulMM)]

 

[AeroFranz]

Indeed, some of these side-by-side double-bubble configurations are pretty old...inlcuding the boundary-layer ingestion aspect.
The D8 also features a cambered fuselage shape intended to carry over some lift from the wings onto the fuselage. Typically there is a 'dip' in lift distribution where the wings meet the fuselage. It originally featured a largely unswept high aspect ratio wing to promote laminar flow, but this was dropped as a concession to operating at higher speeds, more consistent with this class of airliner.
BLI was not (and until demonstrated still isn't) practical until you have distortion tolerant fan blades. Remains to be seen if Pratt's and GE's efforts in this field come to fruition.

 

[TomcatViP]

In the later case they might have traded BLI for Natural Laminar Flow with the engine providing momentum (hence higher laminar conditions) at the fuselage end. Don't forget that a bi-lobbed fuselage (side by side) imparts a blunt boat tail with the negative effects on drag.

With the outside flow of air, the position of the engines, the tail trap, they have an ejector configuration, increasing NLF, augmenting thrust and reducing the needed size of the tail plane (downward lift) hence trim drag...
BLI won't pass the rendered views IMOHO as you have suggested.

 

[bobbymike]

Courtesy of Graham Warwick AW&ST

Flying in formation with future? @Boeing 737 MAX on display alongside @AuroraFlightSci D8 ultra-efficient airliner concept #AiaaAviation - same mission, but drag-reducing boundary layer ingestion makes D8 look quite different to today’s airliners

 

[sienar]

From a NASA pdf

 

[TomS]

Interesting paper on the D8 design.

 

[galgot]

Image taken from this other interesting paper :

https://www.icas.org/ICAS_ARCHIVE/ICAS2018/data/papers/ICAS2018_0875_paper.pdf

 

[cluttonfred]

I do see one fundamental flaw in this approach. Modern airliners get away with using just two engines even on long transoceanic flights because the engines are normally operated at far less than maximum power in cruise, the flight could be continued (at least to an emergency location) with just one engine at a high throttle setting, and the widely separated engines and distinct systems such that even a catastrophic failure of one engine is unlikely to damage the other one. With two engines side-by-side in the tailcone, it seems far more likely that catastrophic failure of one engine would damage the other one as well.

 

[Moose]

I do see one fundamental flaw in this approach. Modern airliners get away with using just two engines even on long transoceanic flights because the engines are normally operated at far less than maximum power in cruise, the flight could be continued (at least to an emergency location) with just one engine at a high throttle setting, and the widely separated engines and distinct systems such that even a catastrophic failure of one engine is unlikely to damage the other one. With two engines side-by-side in the tailcone, it seems far more likely that catastrophic failure of one engine would damage the other one as well.

Indeed. There's also a greater risk that an uncontained failure damages the critical control surfaces given the placement of the fans. While this study is certainly providing useful data, I think we'll more likely see a half-step, like the concepts adding a boundary-ingesting tail engine to a more conventional twin design, or a move directly to distributed electric propulsion, rather than a fully operational D8.